<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Title</title>
 <style>
  *{
   margin: 0;
   padding: 0;
  }
  img{
    width: 200px;
   
  }
  #div1{
   width: 640px;
   height: 120px;
   margin: 100px auto;
   background-color: #646464;
   position: relative;
   overflow: hidden;
  }
  #div1 ul{
   position:absolute;
   left:0;
   top:0;
   overflow: hidden;
   background-color: #3b7796;
  }

  #div1 ul li{
   float: left;
   width: 160px;
   height: 120px;
   list-style: none;
  }
 </style>

 <script>
  window.onload = function(){
   var oDiv = document.getElementById('div1');
   var oUl = document.getElementById('ul1');
   var speed = 5;//初始化速度

   oUl.innerHTML += oUl.innerHTML;//图片内容*2-----参考图（2）
   var oLi= document.getElementsByTagName('li');
   oUl.style.width = oLi.length*160+'px';//设置ul的宽度使图片可以放下

   var oBtn1 = document.getElementById('btn1');
   var oBtn2 = document.getElementById('btn2');


   function move(){
    if(oUl.offsetLeft<-(oUl.offsetWidth/2)){//向左滚动，当靠左的图4移出边框时
     oUl.style.left = 0;
    }

    if(oUl.offsetLeft > 0){//向右滚动，当靠右的图1移出边框时
     oUl.style.left = -(oUl.offsetWidth/2)+'px';
    }

    oUl.style.left = oUl.offsetLeft + speed + 'px';
   }

   oBtn1.addEventListener('click',function(){
    speed = -5;
   },false);
   oBtn2.addEventListener('click',function(){
    speed = 5;
   },false);

   var timer = setInterval(move,30);//全局变量 ，保存返回的定时器

   oDiv.addEventListener('mouseout', function () {
    timer = setInterval(move,30);
   },false);
   oDiv.addEventListener('mousemove', function () {
    clearInterval(timer);//鼠标移入清除定时器
   },false);
  }
 </script>
</head>
<body>
 <input id="btn1" type="button" value="向左">
 <input id="btn2" type="button" value="向右">
 <div id="div1">
  <ul id="ul1">
   <li><img src="./upload/eason.png"></li>
   <li><img src="./upload/jackie.png"></li>
   <li><img src="./upload/jay.png"></li>
   <li><img src="./upload/peng.png"></li>
  </ul>
 </div>
</body>
</html>
